Referring to FIG. 1, a conventional metallization process of semiconductor device will be discussed.
An intermediate insulating layer 12 is formed on a semiconductor substrate 10 having a junction region 11. And then, a contact hole H is formed by etching the intermediate insulating layer 12 so as to expose a predetermined portion of the junction region 11. A first Ti layer 13 as a glue layer is deposited on the intermediate insulating layer 12 and at bottom and inner surfaces of the contact hole H, and successively a first TiN layer 14 as a barrier metal is deposited by a sputtering technology. Herein, the first Ti layer 13 serves for improving the adhesive characteristics between the surface of semiconductor substrate 10, the intermediate insulating layer 12 and the first TiN layer 14. The barrier metal, i.e. the first TiN layer 14 restrains electromigration between the semiconductor substrate 10 and a metal wiring layer to be formed later thereby preventing junction spiking in the junction region 11. Afterward, the Rapid Thermal Annealing(RTA) is performed and then, a titanium silicide layer 13a is formed at an interface of the junction region 11 and the first Ti layer 13. Next, a second Ti layer 15 as a glue layer is deposited on the top surface of the first TiN layer 14. Herein, the second Ti layer 15 serves for improving the adhesive characteristics between a metal wiring layer to be formed later and the first TiN layer 14. A metal wiring layer 16 is formed on the second Ti layer 15. To prevent silicon atoms' migration from the junction region 11 to metal wirings, an alloy layer of aluminum with silicon can be used for the metal wiring layer 16. A second TiN layer 17 as an anti-reflective coating layer is formed on the metal wiring layer 16.
When a predetermined heat, for example at temperature of above 35.degree. C., is applied to the second Ti layer 15 and the metal wiring layer 16, they easily react each other and a TiAl.sub.3 compound 15a is precipitated therebetween. At this time, the TiAl.sub.3 compound 15a has a high resistance that increases the resistance in the metal wirings, which also causes signal delays in semiconductor device. Furthermore, some portions of the metal wiring layer 16 are left behind thereby increasing current density. Accordingly, reliability in the metallization is degraded.
Also, as the semiconductor device is getting integrated, the contact size becomes smaller. Accordingly, it is difficult for the aluminum layer formed by the sputtering technology to fill up the narrow inner space of the contact region H. Therefore, a void is formed or the metal wiring layer is disconnected within the contact hole H.
Furthermore, when the aluminum alloy layer with silicon is used as a metal wiring layer for preventing the electromigration, silicon atoms in the alloy layer are precipitated in the shape of silicon nodule during sequential annealing processes. For the above reasons, reliability in the metallization is degraded.